Not applicable.
1. Field of the Invention
The present invention relates generally to devices for placing concrete or other cementitious materials into earth excavations and/or pre-built forms, and more particularly to a concrete hose end insert, and a method of using the same, for slowing the discharge of concrete from a concrete hose end for increased control during placing operations.
2. Discussion of Related Art
The placement of cementitious material in earth excavations or in spaces defined by concrete foundation forms often entails delivering and placing concrete to the defined space through a vertically disposed boom hose. In light construction projects, liquid cementitious material may be pumped through the hose either directly from a concrete mixer or from a standalone pump into which concrete is poured from the truck""s rotating drum mixer. However, in heavy construction, concrete is commonly placed into forms or an excavation using a mobile truck having a boom and an extendable flexible hose mounted on a power driven hose reel and directed by a hose boom, as is described, for example, in U.S. Pat. No. 5,256,005 to Beck, III. More commonly, the mobile concrete pumping truck has an extendable boom and an articulating steel boom pipe extending the length of the boom through which the concrete flows. A flexible hose is attached to the end of the steel boom pipe, usually either a single segment of hose 12xc2xd feet in length (3.81 meters) or two 12xc2xd foot hose segments for a total of 25 feet (7.62 meters). The flexible hose hangs vertically so that the end of the hose is directly over the placement site. Ready-mix concrete is pumped through the boom pipe and into the desired space through the end of the flexible hose. Accordingly, in the typical concrete pouring operation using a mobile pumping truck, there is a vertical free fall of concrete of at least 12xc2xd feet (7.62 meters) before the concrete is discharged out the end of the hose. Even with this minimum of free fall the concrete free falls out at a rapid rate making control of delivery difficult and heavily impacting ground and forms. Depending on the layout of the job site, the boom pipe and flexible hose may need to be combined so that there is a much greater distance of concrete free fall before discharge. When the placement space is close to the pumping truck, it may require that the boom be in a generally upright attitude. When a long boom is used for the operation and must be deployed essentially vertically, it is possible that the concrete must fall in excess of 100 feet (30.5 meters) before discharge.
Thus, regardless of the actual free fall immediately before discharge, the velocity of the concrete leaving the hose end is quite high. This cannot be slowed by reducing the pumping rate, for once the concrete begins its free fall down any descending segment of boom pipe and ultimately through the flexible hose, it falls according to the laws of gravity and is slowed only by incidental contact with the sides of the hose and boom pipe. As a result, the concrete drops into its placement site at a high rate of speed and with considerable force. This can damage forms, cause splattering of concrete outside the defined placement space, and cause extensive concrete flow in open footings. The problem applies to concrete of any practicable slump test. It results in wasted concrete and requires costly, time consuming clean up. On occasion it may result in damage to nearby structures. Furthermore, the fluid pressure of the flowing mud makes control of the hose end difficult. Surges during pumping can cause the hose end to whip around dramatically and dangerously.
Devices have been proposed to reduce concrete splashing when the fluid concrete is poured directly from a concrete truck and to foundation forms through a chute positioned at the back of the truck beneath the mixing drum. For example, U.S. Pat. No. 5,868,180 to Hendrickson teaches a concrete form splash funnel for directing the flow of fluid concrete to the form for a concrete wall or a concrete block wall. The funnel is preferably a unitary plastic piece that can be nested with other funnels for easy storage. As noted, however, this device is designed for placement under the end of a discharge chute beneath the rotating drum of a concrete mixing truck. It is not adaptable for use on the end of a boom hose.
Devices have also been proposed to slow the velocity of concrete pouring from a boom hose. For example, a short steel S-pipe coupled to the hose end came into common use in the industry for a brief period. The two 90 degree bends in the pipe successfully slowed the discharge of mud, but the force of the flowing concrete plugging in the S-pipe often caused the pipe to whip around in a violent fashion. Additionally, residual concrete would set in the lower portion of the first bend during breaks in the operation, causing a dangerous backup of concrete when pouring was resumed. The advantages of this device are easily balanced by its disadvantages.
A pin hose manufactured by Putzmeister of Germany met with greater success and had fewer serious disadvantages than the S-pipe. The pin hose comprises a tapered tip having a plurality of inwardly disposed tines, each of said tines fabricated from a flexible polymer.
However, as with the S-pipe, the pin hose frequently retains vestigial concrete when pouring is suspended or halted. If this concrete sets before pouring resumes, the hose can plug and cause a sudden and dangerous discharge of concrete.
As yet there is no known device adapted to control the flow of fluid concrete through a hose by introducing a simple insert within the interior of the hose end.
The concrete hose end insert of the present invention provides a means to control the velocity of concrete discharged from a concrete hose, and therefore to control the rate of concrete discharge from a hose end. The inventive apparatus comprises an annular base member having a plurality of integrally connected, spaced-apart clamp members positioned around the annulus and adapted for coupling to a concrete hose end. The hose insert includes a vertical insert member having a lip or flange at its upper end. The lip has a hole for the connection of a chain. The clamp members comprise steel posts welded to the outer circumferential surface of the annular base member, and each of the posts has a threaded aperture through which a metal bolt is screwed for adjustably tightening against the exterior circumference of the concrete hose end.
The hose insert causes turbulence in the flow of concrete immediately prior to its discharge from the hose end. The turbulence and the resulting interruption in flow cause the free falling concrete to recombine or compact slightly while still in the hose. When using the inventive apparatus, concrete discharges at a lower velocity and more homogenized state, and therefore causes minimal splattering and is easily controlled in its placement.
A method of using the above-described apparatus is also disclosed, said method directed to controlling the flow rate of concrete from a concrete hose by recompressing and partly compacting the free falling concrete just inside the discharge end of the hose.